What equations are linear and non-linear

6x^2+6=6
6x+6=6
6x^4=5x
6x+6=11x

Linear equations:

6x + 6 = 6
6x + 6 = 11x

Non-linear equations:
6x^2 + 6 = 6
6x^4 = 5x

Find linear and non linear

2x+7x=-2
Square root of x =2+7x
2x^5-2x=6
3x-2=7

Linear equation:

3x - 2 = 7

Non-linear equations:
2x + 7x = -2 (simplifies to 9x = -2)
Square root of x = 2 + 7x
2x^5 - 2x = 6

The equations that are linear are:

1) 6x + 6 = 6
2) 6x + 6 = 11x

The equations that are non-linear are:

1) 6x^2 + 6 = 6
2) 6x^4 = 5x